Particle-phonon interactions inCf248andCf249

The extent of particle-photon mixing in ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cf}$ and ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ has been determined using the ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}(d, t)$ and ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}(d, d^{\prime })$ reactions. $K^{\pi }=2^{-}$ bands were identified at 593 and 1477 keV in ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cf}$. Since the only $K^{\pi }=2^{-}$ neutron two quasiparticle configuration expected below 2 MeV in ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cf}$ is ${\left\{{\frac{9}{2}}^{-}\mathrm{}\right[734];{\frac{5}{2}}^{+}\mathrm{}[622\left]\right\}}_{2-}$, the second $K^{\pi }=2^{-}$ band is considered to be predominantly of phonon character. In ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ a $K^{\pi }={\frac{5}{2}}^{+}$ band at 145 keV, known from decay scheme studies, receives a measurable population in the ($d, d^{\prime }$) reaction. The phonon admixture in the ${\frac{5}{2}}^{+}$ state which results from the $\left\{{\frac{9}{2}}^{-}\mathrm{}\right[734]\mathrm{}\otimes 2^{-} \mathrm{phonon}\}$ configuration was determined to be (29±5)%. The collective admixture in the ${\frac{5}{2}}^{+}$ state was also calculated from an octupole particle-hole interaction and was found to be 35%, in good agreement with the experimental value. The anomalously low energy of the ${\frac{5}{2}}^{+}$ state could not be entirely reproduced by this calculation.